This invention relates to a system for controlling the power delivered to HID and fluorescent light systems and, more particularly, to reducing the voltage to the lighting systems during periods of peak demand in the electrical power network and other prescribed periods of time to maximize efficiency and meet the guidelines imposed by regulatory parties.
In previous years, there have been periods of time in which the power available on certain electrical power grid networks is insufficient to supply the loads on the system. This is particularly true during the summer months when increased demands are made on electrical power systems by air conditioning and the like. In order to alleviate this problem, power companies have been required to mandate power limits on commercial and industrial customers. In particular, large grocery stores and retail complexes have been required to lower the power consumption of fluorescent lighting systems during the peak demand hours. Significant fines are placed on these customers if they exceed the power consumption mandated during the peak demand periods.
In the case of fluorescent and other commercial lighting systems, it is known to use autotransformers in the power supply to step the voltage up or down. It is known to manually change taps on an autotransformer to increase or decrease the voltage supply. However, to do this requires that the power system be shut down, physically unbolt the wire on the autotransformer, and move the wiring to new taps. The switching of these autotransformers is also typically done using mechanical relay contacts. Toroidal transformers have also been used in power control systems for controlling lighting using resistance or mechanical relay contact switching. Because there is a certain amount of energy in a transformer, current spikes occur during switching using mechanical contacts so that the contacts wear out and burn up beyond use. Therefore, the use of manual switching or mechanical contact relay switching in transformer systems has been an obstacle to the use of these systems. U.S. Pat. No. 6,191,568 B1 discloses a load voltage and power control supply system particularly suitable to street lighting systems. The power control system is able to act as a voltage stabilizer, as well as a control power reduction system, to operate spaced lighting from a single location. The controller uses a series of stepped down decreasing output levels between a high voltage and a low voltage to stabilize the autotransformer voltage.
U.S. Pat. No. 5,528,110 provides a voltage reduction apparatus designed to overcome the prior art problems of magnetic field flux, induced harmonic distortion, and heating wherein a bucking coil is wound in parallel to a common winding of the autotransformer to cancel any magnetic induced voltage in the common winding during switching.
U.S. Pat. No. 4,189,664 discloses a power control unit for automatically controlling the power consumption in a lighting load located between the power source and the load. The power control unit functions to reduce the voltage delivered to the load by applying one of a plurality of taps from an autotransformer to a lighting load wherein the switching unit is interposed between the input power and the load. U.S. Pat. No. 4,431,948 discloses a voltage reducing apparatus applied to a load utilizing an autotransformer and relay switching between the common winding and series winding of the autotransformer which avoids the problem of including a switching apparatus in the direct current path between the input power source and the load as disclosed in the former patent.
U.S. Pat. No. 5,477,113 discloses a dimmer for a halogen light which typically use a toroidal transformer to reduce house voltage to the 12 volts normally utilized by halogen bulbs. The transformer is provided with a variety of taps for stepping down the voltage by use of a stepping motor.
U.S. Pat. No. 3,719,857 discloses a dimmer for fluorescent, ultraviolet, or other gas discharge lighting using a dimmer or blinking ballast transformer. The variable power system is controlled by an audio signal apparently to provide a visual lighting display synchronous with sound produced by a speaker driven by an amplifier.
While a number of solutions have been provided to the problems encountered in power reduction systems caused by autotransformers and mechanical switching, considerable attention still needs to be given to the problems. In particular, the provision of the power reduction systems for lighting and the like wherein the power reduction system can be incorporated with other sophisticated electronics such as those found in environmental control panels is a problem to which considerable attention need be given.
Accordingly, an objective of the present invention is to provide an improved power reduction system for HID and fluorescent systems to reduce the voltage in order to meet the limitations placed on power consumption during peak demand and other periods.
Another object of the present invention is to provide a power reduction system for limiting the power to lighting and other systems which is light in weight, as well as providing cooler, quieter, and more efficient operation.
Another object of the present invention is to provide an improved power reduction system for electrical loads, particularly fluorescent lighting and the like, wherein a solid-state switching circuit is employed with toroidal transformers to provide a range of selectable voltage levels to reduce harmful current transients inherent in such transformer systems.